docs: public README + generic CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: install rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+
+      - name: fmt
+        run: cargo fmt --all --check
+
+      - name: clippy
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: build
+        run: cargo build --all-targets
+
+      - name: test
+        run: cargo test